This invention relates generally to air pumps, and more particularly, is directed to a portable air pump assembly for inflating the tires of an automotive vehicle.
It is often necessary or desirable to inflate one or more tires of an automotive vehicle, but in many instances, there are no air pumps or compressors available. For example, when changing a flat tire on an automobile stranded on a deserted road, it is sometimes discovered too late that much of the air in the spare tire has escaped. As another example, it may be necessary to inflate a tire late at night when many service stations are closed.
For these and other reasons, portable air pumps have been developed which can easily be carried in the automotive vehicle. Such air pumps generally operate from the battery of the vehicle, either directly or through the cigarette lighter. An example of such a portable air pump is found in U.S. Pat. No. 4,614,479. In this patent, a pressure gauge includes a pressure setting pointer used to set a desired pressure. A pressure indicating pointer contacts the pressure setting pointer when the preset pressure has been reached, and thereby shuts off the motor through electric logic circuitry. However, because of the moving pressure indicating pointer and electric logic circuitry, this device is not so reliable in operation.
U.S. Pat. No. 4,080,105 discloses a tire inflator that uses a knob to adjust the spring pressure on a piston. When the tire has been inflated to the desired pressure, the piston is moved against the force of the spring, and at the same time, contacts and moves a linkage member that pivots and therefore disengages a latch from a switch actuating lever, thus allowing a spring loaded switch to return to its open position, thereby shutting off an air pump motor. This device, however, through the various linkages and levers, is relatively complex from a mechanical standpoint, with many moving parts, and may not be so reliable in operation. Further, this tire inflator is formed in a gun configuration with a trigger actuator, and is only used to inflate bicycle tires. Furthermore, it utilizes an electric plug which must be plugged into an electric outlet.
Other devices of similar or less relevant importance are disclosed in U.S. Pat. Nos. 1,647,818; 2,062,220; 2,217,288; 2,684,685, 3,844,319; 3,885,892; 4,187,058; 4,197,895; 4,212,334; 4,389,166; 4,424,006; 4,583,566; and 4,621,984.